Various closure and valve mechanisms are used to selectively control the flow of a liquid, such as chemicals, food items, and the like from a disposable package such as flexible collapsible bag. In many of these closures, the valve opens is opened as a dispensing connector is connected to the closure and closes as it is disconnected therefrom to prevent the liquid from draining from the bag. Generally, these types of closures utilize a spring or other mechanical bias member for closing the valve. Unfortunately, these mechanical bias members can have a slow response time, especially when held in an open position for a long period of time, or they can be stressed beyond their elastic limits. As such, liquid can leak through the valve when the valve is disconnected from the dispenser.